Abstract: In this paper the diameter between tubercles of iliac crests (X1), diameter between anterior superior iliac spines (X2 ), diameter between greater trochanters (X3) and diameter between ischial tubercles (X4) of 126 women, who are at child bearing age and are not pregnant, were acted as the independent variable. The dependent variable and the trans verse diameter of middle pelvis (Y ?) were evaluated. The multidimensional regression equation was calculated: Y ?= 6.89 + 0.05(X1)+0.12(X2) + 0.23(X3) + 0.77(X4). The external sacro-pubic diameter (X1) and inclination of pelvis (X2) were acted as the independent variable, and the dependent variable-the sagittal diameter (Y ?)-was figured, The regression equation was as follows: Y ? = 6.09十0.39 (X1) - 0.05(X2). These two regression equations were tested by the analysis of variance. F values are 40.69 and 8.26 respectively. They both are of high significance, so they can be used in clinical practice to estimate the diametes of middle pelvis, replacing radiogrammetry.

Key words: Regression equation; Middle pelvis; External measurement of pelvis